function shareThisBook(bookID) {
  var winWidth = 320; var winHeight = 400;
  var leftPos = Math.round((screen.availWidth - winWidth)/2).toString();
  var topPos = Math.round((screen.availHeight - winHeight)/2).toString();
  winURL = a = "/books/ShareThis/sharethis_popup.asp?d=" + bookID + "&r=" + location.href;
  winDefinition = "width=" + winWidth + ",height=" + winHeight + ",left=" + leftPos + ",top=" + topPos + ",menubar=0,toolbar=0,status=1,resizable=1,scrollbars=0,dependent=0";
  w = window.open(winURL,'ShareThisBook',winDefinition);
  return false;
  }